The present invention relates to the field of plant molecular biology and gene silencing. More particularly, the present invention relates to gene silencing of Sugar-dependent 1 (JcSDP1) in Jatropha curcas. JcSDP1 encodes a patatin-domain triacylglyerol lipase. Silencing of JcSDP1 enhances seed oil accumulation in J. curcas. 
The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference, and for convenience are referenced in the following text by author and date and are listed alphabetically by author in the appended bibliography.
The diminishing stock of fossil fuel has catalyzed a soaring demand for renewable energy sources world-wide. To meet this demand active research has been initiated relating to solar, wind, tidal and geothermal power generations during the last several decades. Likewise, there is also an increasing focus on biofuels, which are energy sources derived from renewable biomass. There are two main types of biofuels: bioethanol and biodiesel, which are generally used as gasoline and diesel additives, respectively. Bioethanol is mainly produced by fermentation using sugar or starch derived from crops such as sugar cane and corn. Biodiesel, on the other hand, is obtained by trans-esterification of plant oils and animal fats. In 2010, the global biofuel production reached 105 billion liters and provided 2.7% of the world's energy needs for transportation. It has been forecast that biofuel may account for more than a quarter of the world's demand for transportation fuels by 2050 (1).
Biodiesel is generally produced from oil seed crops such as rape in temperate countries and oil palm in the tropics. In the past several years, a small tree called Jatropha curcus grown in the tropical and subtropical regions has emerged as an attractive candidate crop for biodiesel production. Jatropha has several interesting attributes making it suitable for consideration as a biodiesel plant. Jatropha seeds contain up to 40% oil consisting of approximately 75% unsaturated fatty acids (2, 3), with a high level (around 47%) of linoleic acid (C18:2) (4). In addition to having a high oil content and favorable oil composition for biodiesel, Jatropha plants have a short gestation period and adapt well to a wide range of agro-climatic conditions (5, 6). Moreover, its ability to grow on marginal land reduces the possibility that Jatropha may compete with food crops for arable land.
Because of Jatropha has just been recently been domesticated much work remains to be done to improve its agronomic traits either by traditional breeding or by gene technology.
Given the commercial interest in Jatropha seed oil, it is not surprising that the immediate focus is on seed oil content and quality. With respect to the latter trait, Qu et al. (7) have recently reported that gene silencing of JcFAD2 can greatly enhance the proportion of oleic acids in seeds of transgenic Jatropha. Here, we addressed the issue of increasing levels of oil accumulation in Jatropha seeds by genetic modification.
Plant oil in seeds is stored as triacylglycerol (TAG) consisting of three fatty acid chains (usually C16 or C18) covalently linked to glycerol. Depending on the plant source, TAGs may contain fatty acids of different chain lengths and degree of saturation and the fatty acids may be decorated with diverse modifications. Plant TAGs are generally stored in small organelles called oil bodies which are assembled in developing seeds, flower petals, pollen grains and fruits of a huge number of plant species (8, 9). During seed germination TAGs are hydrolyzed into fatty acids and glycerol and this reaction is catalyzed by TAG lipases, which are widely distributed in plants but also found in animals and microorganisms (10). Among the known lipases, the unorthodox patatin-like TAG lipases (PTLs) are oil body-associated enzymes that play a major role in the initiation of TAG degradation in yeast, mammals and insects (11, 12). During seed germination, TAG lipases initiate TAG degradation into glycerol and free fatty acids and the released fatty acids are consumed through the beta-oxidation pathway which releases energy for early seedling growth (13, 14).
Recently, Eastmond (15, 16) has shown that the sugar-dependent 1 (SDP1) of Arabidopsis encodes a patatin-like acyl hydrolase domain. The encoded protein, SDP1, is specifically responsible for the first step of TAG degradation during Arabidopsis seed germination. This enzyme is also able to associate with oil body surface as well as the other reported PTLs. A T-DNA insertion SDP1 mutant allele, sdp1-5, displayed growth retardation on a sugar-deficient medium due to the deficiency of glycerol and free fatty acids, which are products of TAG degradation (15, 16). The study of Eastmond (15, 16) showed an accumulation of clustered oil bodies in seedling cotyledons and a higher TAG levels in sdp1-5 than WT (Col-0).
It is desired to increase seed oil content in Jatropha which would be an important agronomic trait for this biodiesel crop.